Self-piercing clinch nut

ABSTRACT

A self-clinching fastener for attachment to a plastically deformable metal panel includes a body portion with a central axis and a central pilot portion extending from the body portion and coaxial with the central axis. The body portion forms a generally annular-shaped end face adjacent the central pilot portion and a groove defined in the end face encircling the central pilot portion. The groove has an inclined inner wall forming an undercut and an inwardly inclined bottom wall such that the groove has an increasing depth in a direction toward the undercut. The inclined bottom wall is formed by a plurality of generally flat faces and the inclined inner wall is formed by a plurality of generally flat faces which are aligned with the faces of the bottom wall. The fastener further includes a plurality of spaced apart lugs encircling the central pilot portion and axially extending from at least one of the end face and the groove. The lugs form abutments to improve torsional resistance of the fastener.

BACKGROUND OF THE INVENTION

The present invention generally relates to self-attaching fasteners and,more specifically to clinch nuts and installation tooling therefor.

Self-attaching fasteners are used in many industries such as, forexample, the automotive and appliance industries to secure variouscomponents to metal panels. When clinch nuts are attached to the metalpanels, screws or bolts are threaded into the clinch nuts and tightenedto prescribed torque values. During installation, the clinch nuts musthave sufficient rotational resistance to keep them from rotatingrelative to the metal panels when the screws are inserted and tightened.During service, the clinch nuts must have sufficient pull-throughresistance to keep them from pulling out of the metal panel whenexternal forces such as, for example, vibration or other tensile forcesare applied.

A clinch nut typically includes a central pilot or punch portion whichat least partially extends into an opening in a metal plate or panel.When the clinch nut is self piercing, the central pilot portioncooperates with tooling to form the opening in the metal panel whenattaching the clinch nut to the metal panel. The clinch nut is attachedto the metal panel by a die member which forms a mechanical interlockbetween the clinch nut and the metal panel. The die member typicallydeforms the metal panel about the opening into an annular groove of theclinch nut which encircles the pilot portion and/or deforms the pilotportion of the clinch nut over the metal panel to entrap the metalpanel.

For example, U.S. Pat. No. 3,053,300 discloses a clinch nut having acentral pilot portion which extends through a pre-formed opening in ametal panel and is folded over to stake the periphery of the opening.The deformation of the central pilot forces the metal panel to conformto an undulating surface of the annular groove and to form the interlockbetween the clinch nut and metal panel. While this clinch nut may have arelatively high pull-out resistance, the deformation of the centralpilot can easily distort the internal threads of the clinch nut.

One approach to eliminate distortion of the internal threads whendeforming the pilot is to deform the metal panel to form the interlockrather than the pilot of the clinch nut. For example, U.S. Pat. Nos.3,878,599 and 4,690,599 each disclose a clinch nut having an undercut oneither the inner or outer wall of the groove. Material of the metalpanel is forced into the undercut to improve the interlock formedbetween the clinch nut and the metal panel. With relatively thin metalpanels, however, very little material is forced into the undercut,resulting in a relatively low pull-out resistance.

One approach to increase the pull-out resistance of clinch nuts of thistype is to form a double-undercut groove. For example, U.S. Pat. No.5,340,251 discloses a clinch nut having undercuts in both the inner andouter walls so that the annular groove is “dove-tail” shaped in crosssection. The metal panel is forced into both of the undercuts to form animproved interlock between the clinch nut and metal panel. Thedeformation of the metal panel required to fill both undercuts, however,is difficult to obtain using conventional forming techniques, resultingin inconsistent pull-out resistance.

An additional problem with the above-noted self-clinching fasteners isthat they typically to not function well with thin metal panels, thatis, panels of 3 mm or less. Accordingly, there is a need in the art foran improved clinch nut which can be reliably and consistently attachedto a thin metal panel having sufficient pull-out strength, sufficientrotational resistance, and without having distortion of the internalthreads. Additionally, there is a need for an improved die member forinstalling a clinch nut in a thin metal panel having sufficient pull-outstrength, having sufficient rotational resistance, and without havingdistortion of the internal threads. Furthermore, there is a need forboth the clinch nut and the die member to be relatively inexpensive toproduce and relatively easy to use.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a self-clinching fastener for attachmentto a plastically deformable metal panel which overcomes at least some ofthe above-noted problems of the related art. According to the presentinvention, the self-clinching fastener includes a body portion with acentral axis and a central pilot or punch portion extending from thebody portion and coaxial with the central axis. The body portion forms agenerally annular-shaped end face adjacent the central pilot portion anda groove defined in the end face encircling the central pilot portion.The groove has an inclined inner wall forming an undercut and aninwardly inclined bottom wall such that the groove has an increasingdepth in a direction toward the undercut. The inclined bottom wall isformed by a plurality of generally flat faces, and a plurality of spacedapart lugs encircling the central pilot portion and axially extendingfrom at least one of the end face and the groove. The lugs formabutments to improve torsional resistance of the fastener.

According to another aspect of the present invention, the self-clinchingfastener includes a body portion with a central axis and a central pilotportion extending from the body portion and coaxial with the centralaxis. The body portion forms a generally annular-shaped end faceadjacent the central pilot portion and a groove defined in the end faceencircling the central pilot portion. The groove has an inner wallformed by a plurality of generally flat faces and a bottom wall formedby a plurality of generally flat faces. The faces of the bottom wall arealigned with the faces of the inner wall. A plurality of spaced apartlugs encircle the central pilot portion and axially extend from at leastone of the end face and the groove. The lugs form abutments to improvetorsional resistance of the fastener. Preferably, the groove furtherincludes an outer wall formed by a plurality of generally flat facesaligned with the faces of the inner wall and the bottom wall.

According to yet another aspect of the present invention, a method ofattaching a self-clinching fastener to a plastically deformable metalpanel includes coaxially positioning the fastener and a die member onopposite sides of the metal panel at a position in which the fastener isto be secured to the metal panel. The fastener and the die member areoriented so that a plurality of inclined faces in a groove of thefastener and a cooperating plurality of inclined faces of the die memberare circumferentially aligned. The die member and the fastener are thenrelatively moved toward one another in an axial direction to deform aportion of the panel into the groove of the fastener by coining thepanel between the inclined faces of the fastener and the inclined facesof the die member and on opposite sides of lugs configured to improvetorsional resistance of the fastener until a secure mechanical interlockis formed between the fastener and the panel.

According to even yet another aspect of the present invention, aself-clinching fastener for attachment to a plastically deformable metalpanel includes a body portion with a central axis and a central pilotportion extending from the body portion and coaxial with the centralaxis. The body portion forms a generally annular-shaped end faceadjacent the central pilot portion and a groove defined in the end faceencircling the central pilot portion. The groove has an inclined innerwall forming an undercut and an inwardly inclined bottom wall such thatthe groove has an increasing depth in a direction toward the undercut.The inclined bottom wall is inclined at an angle greater than 2 degreesand less than about 50 degrees relative to a plane perpendicular to thecentral axis. The fastener further includes a plurality of spaced apartlugs encircling the central pilot portion and axially extending from atleast one of the end face and the groove. The lugs form abutments toimprove torsional resistance of the fastener. Preferably, the inclinedbottom wall is inclined at an angle of about 20 degrees relative to theplane perpendicular to the central axis.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

These and further features of the present invention will be apparentwith reference to the following description and drawings, wherein:

FIG. 1 is a perspective view of a clinch nut according to a firstembodiment of the present invention;

FIG. 1A is a perspective view of a clinch nut according to a variationof the clinch nut of FIG. 1;

FIG. 2 is a top plan view of the clinch nut of FIG. 1;

FIG. 3 is a sectional view taken along line 3—3 of FIG. 2;

FIG. 3A is a sectional view similar to FIG. 3 but of the clinch nut ofFIG. 1A;

FIG. 4 is a bottom plan view of die for installing the clinch nutaccording to the present invention;

FIG. 5 is a sectional view taken along line 5—5 of FIG. 4;

FIGS. 6A to 6C are elevational views, in cross-section, showing variousstages of installation of the clinch nut of FIG. 1 using the die of FIG.4;

FIG. 7 is a perspective view of a clinch nut according to a secondembodiment of the present invention;

FIG. 8 is a top plan view of the clinch nut of FIG. 7;

FIG. 9 is a sectional view taken along line 9—9 of FIG. 8;

FIG. 10 is a perspective view of a clinch nut according to a thirdembodiment of the present invention;

FIG. 11 is a top plan view of the clinch nut of FIG. 10;

FIG. 12 is a sectional view taken along line 12—12 of FIG. 11;

FIG. 13 is a perspective view of a clinch nut according to a fourthembodiment of the present invention;

FIG. 14 is a top plan view of the clinch nut of FIG. 13;

FIG. 15 is a sectional view taken along line 15—15 of FIG. 14;

FIG. 16 is a perspective view a clinch nut according to a fifthembodiment of the present invention;

FIG. 17 is a top plan view of the clinch nut of FIG. 16;

FIG. 18 is a sectional view taken along line 18—18 of FIG. 17;

FIG. 19 is a perspective view of a clinch nut according to a sixthembodiment of the present invention;

FIG. 20 is a top plan view of the clinch nut of FIG. 19;

FIG. 21 is a sectional view taken along line 21—21 of FIG. 20;

FIG. 22 is a perspective view of a clinch nut according to a seventhembodiment of the present invention;

FIG. 23 is a top plan view of the clinch nut of FIG. 22; and

FIG. 24 is a sectional view taken along line 24-24 of FIG. 23.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1-3 illustrate a self-piercing clinch nut 10 according to a firstembodiment of the present invention for attachment to a plasticallydeformable metal plate or panel. It is noted that while the illustratedembodiment is a nut, other self-clinching fasteners such as, forexample, self-clinching studs are within the scope of the presentinvention The clinch nut 10 has a body portion 12 and a pilot or punchportion 14 extending from one end of the body portion 12, and a threadedhole or bore 16 axially extending through both the body portion 12 andthe punch portion 14.

The punch portion 14 is generally smaller than the body portion 12 toform a generally annular-shaped surface or end face 18 for engaging ametal panel as described in more detail hereinafter. The panel-engagingsurface 18 is preferably substantially perpendicular to the central axis20. A generally annular-shaped groove 22 is formed in the panel-engagingsurface 18 and is preferably adjacent and/or contiguous with the punchportion 14. The groove 22 preferably does not extend to the outer edgeof the panel-engaging surface 18 so that the panel-engaging surface 18forms a lip 24 at the outer periphery of the groove 22. The lip 24 is anarrow bearing surface band which, while uniform in width, presents acontinuously variable radial swept area to maximize the torsionalintegrity of the clinch nut 10. The groove 22 is preferably formed by abottom wall 26, an inner wall 28, and an outer wall 30.

The illustrated bottom wall 26 is inwardly angled or inclined toward theinner wall 28, that is the groove 22 increases in depth when radiallymoving from the outer periphery of the bottom wall 26 to the innerperiphery of the bottom wall 26. The bottom wall 26 is preferablyinclined at an angle of greater than 2 degrees and less than about 50degrees relative to a plane perpendicular to the central axis 20, ismore preferably at an angle of greater than 5 degrees and less thanabout 50 degrees relative to a plane perpendicular to the central axis20, is even more preferably at an angle of about 10 degrees to about 45degrees relative to a plane perpendicular to the central axis 20, and ismost preferably at an angle of about 20 degrees relative to a planeperpendicular to the central axis 20. It should also be obvious that thebottom wall 26 could contain a variety of inclined angles relative toone another on a single nut 10. The angled or inclined bearing surfacemaximizes the extent to which the work-piece cooperates with the clinchnut 10 to resist axial loads which tend to separate the two components.Increasing the angle increases the depth of the groove 22 and thereforethe length of the punch. This “punch length extension” allows the clinchnut to be secured to work-piece thicknesses well below prior art clinchnuts, that is, the clinch nut can be secured to work-pieces havingthicknesses below 1.63 mm. If the angle gets to large, however, thelength of the body portion 12 must be increased and tooling problems arecreated in forming the groove.

The bottom wall 26 is preferably polygonally-shaped wherein it is formedby a plurality of angled or inclined, planer or flat faces or facets 32.The bottom wall 26 is preferably formed by about 6 to about 10 of thefaces 32, and is more preferably formed by about 8 of the faces 32. Thepolygonal-shape provides a non-uniform shape which constricts or coinsthe work-piece material during the clinch-nut setting process, therebygenerating enhanced push-out resistance and torque-out resistance asdescribed in more detail hereinafter. The bearing area is increased byincreasing the number of the faces 32 (note the optimum bearing area isa cone) but this decreases the torsional resistance. When more than 10of the faces 32 are used, the bearing surface begins to approximate acone. When less than 6 of the faces 32 are used, too little bearingsurface is available for adequate bearing loads. The octagon-shape using8 of the faces 8 is a balance point between these two competingrequirements.

The illustrated inner wall 28 is inwardly angled or inclined such thatthe groove 22 forms an undercut in the punch portion 14. The inner wall28 is also preferably polygonally-shaped wherein it is formed by aplurality of angled or inclined, planar or flat faces or facets 34. Theinner wall 28 is preferably formed by about 6 to about 10 of the faces34, and is more preferably formed by about 8 of the faces 34. Asillustrated, the inner wall 28 is most preferably formed by the samenumber of faces 34 as the bottom wall 26 and the faces 34 of the innerwall 28 are preferably circumferentially aligned with the faces 32 ofthe bottom wall 26 and the outer wall 30.

The illustrated outer wall 30 is substantially perpendicular to thepanel-engaging surface 18, that is, the outer wall 30 is substantiallyparallel with the central axis 20. The outer wall 30 is also preferablypolygonally-shaped wherein it is formed by a plurality of planar or flatfaces or facets 36. The polygonal shape of the outer wall 30 enhancestorsional resistance because the outer wall 30 must plow throughwork-piece material for the clinch nut to rotate relative to thework-piece. The outer wall 30 is preferably formed by about 6 to about10 of the faces 36 and is more preferably formed by about 8 of the faces36. As illustrated, the outer wall 30 is most preferably formed by thesame number of faces 36 as the bottom and inner walls 26, 28 and thefaces 36 of the outer wall 30 are preferably circumferentially alignedwith the faces 32, 34 of the bottom and inner walls 26, 28. It is notedthat the outer wall 30 can alternatively have other configurationswithin the scope of the present invention and can even be eliminated byextending the bottom wall 26 to the panel-engaging surface 18 or lip 24(for example, see alternative embodiments illustrated in FIGS. to10-21).

The illustrated body portion 12 has an outer periphery which ispolygonally-shaped wherein it is formed by a plurality of planar or flatfaces or facets 38. The outer periphery is preferably formed by about 6to about 10 faces 38, and is more preferably formed by about 8 faces 38.As illustrated, the outer periphery is preferably formed by the samenumber of faces 38 as the walls 26, 28, 30 of the groove 22 and thefaces 38 of the outer periphery are preferably circumferentially alignedwith the faces 32, 34, 36 of the groove walls 26, 28, 30. It is noted,however, that the outer periphery of the body portion 12 canalternatively have other configurations within the scope of the presentinvention such as, for example, cylindrical. The length of the bodyportion 12 is sized to provide sufficient thread engagement toconsistently break (without stripping the threads) the mating externallythreaded member whose material strength properties are matched to thoseof the clinch nut 10.

In the illustrated embodiment, the inner wall 28 of the groove 22 iscontiguous with the outer periphery of the punch portion 14 so that theinner wall 28 generally forms the outer periphery of the punch portion14. It is noted, however, that the outer periphery of the punch portion14 can have other configurations within the scope of the presentinvention. The outer or free end of the punch portion 14, which isopposite the body portion 12, has a piercing or shearing edge 40 formedthereon. As described in more detail hereinafter, the shearing edge 40cooperates with a die member to perforate or shear a metal plate orpanel during installation of the clinch nut 10 in the metal panel. Thelength of the punch portion 14 is preferably sized to accommodate thework-piece material thickness without protruding beyond the plane formedby the back side of the work-piece as described in more detailhereinafter. The diameter of the punch portion 14 is preferably sized toprovide sufficient column strength to allow the clinch nut 10 to punchits own hole into materials up to 3 mm thick at a maximum hardness of 60on the Rockwell C hardness scale (approximately 50,000 p.s.i. ultimatetensile strength of the work-piece material). It should be obvious thatfor thinner and/or softer materials, these maximum values would beincreased. It should also be obvious that for thicker materials and/orharder materials, the punch portion geometry can be sized to accommodatethe requirements of those work-pieces.

The clinch nut 10 also includes a plurality of locking members or lugs42 for increasing the torque or rotational resistance of the clinch nut10. The lugs 42 are raised lobes or protuberances which axially extendabove the panel-engaging surface 18, the groove 22, or the lip 24 andcircumferentially extend over a limited distance such that abutments 43are formed which impede or resist rotation of the clinch nut 10 relativeto the metal panel. The abutments 43 are preferably perpendicular to therotational motion of the nut. In the illustrated embodiment, the lugs 42are formed by protuberances which axially extend above the groove bottomwall 26 and radially extend across the groove 22 from the groove innerwall 28 to the groove outer wall 30. The upper sides of the lugs 42,which are the sides opposite the bottom wall 26, are generallyperpendicular to the central axis 20 and are generally parallel to thelip 24 but are preferably recessed below the lip 24. The lugs 42 arepreferably circumferentially spaced apart along the bottom wall 26 andthere is preferably a lug 42 centrally located on each face 32 of thebottom wall 26. It is also noted, however, that the lugs 42 may belocated at other positions such as the interface between adjacent faces32 of the bottom wall 26. The cross-sectional shape of the illustratedlugs 42 is rectangular. The cross-sectional shape of the lugs 42,however, may be any other suitable shape.

It is noted that adjacent faces 32 of the bottom wall 26 mayalternatively be joint-free at the corners of the nut body portion 12and jointed at the radial centerlines of the lugs 42. This alternativemay give the area of the groove 22 increased torsional loadingresistance because the abutments 43 would be axially larger andtherefore give more torsional resistance.

For example, an acceptable clinch nut 10 having a thread size of M10×1.5and for work pieces having a minimum thickness of 0.050 inches (1.27 mm)can have a bottom wall 26 with eight facets 32 inclined at an angle ofabout 20°. The facets 32 are aligned with eight facets 34 of the punchportion inner wall 28, eight facets 36 of the outer wall 30, and eightfaces 38 of the body portion outer periphery. The outer wall 30 has aheight of about 0.015 inches to about 0.025 inches. The body portion isabout 0.712 to about 0.730 inches across corners, is about 0.666 toabout 0.674 inches across flats, and has a height of about 0.314 toabout 0.318 inches. The distance between inner edges of the lip 24 isabout 0.600 to 0.606 inches. The punch portion 14 has a height of about0.043 to about 0.047 inches above the lip 24, a diameter of about 0.514to about 0.518 inches, and a base diameter at the bottom wall of about0.484 inches maximum. The lugs 42 have a width of about 0.058 to about0.081 inches.

FIGS. 4 and 5 illustrate a die member 44 according to the presentinvention which is used to attach the clinch nut 10 to a metal panel orplate. The die member 44 has a generally cylindrical-shaped body 46 witha panel-engaging end face or surface 48 which is substantiallyperpendicular to the central axis 50. An axially extending central boreor opening 52 forms a piercing or shearing edge 54 at the inner edge ofthe panel engaging end face 48. The shearing edge 54 is sized and shapedto cooperate with the shearing edge 40 of the clinch nut 10 (FIGS. 1-3)to perforate or shear a metal plate or panel during installation of theclinch nut 10 in the metal panel. The generally annular-shapedengagement end face 48 is sized to cooperate with and/or extend into thegroove 22 of the clinch nut 10. Although in some instances the end face48 may be sized to cooperate with the surface 18 to create aconstriction and pinching action upon the panel 58 thereby trapping andfurther compacting the metal panel 58 into the groove 22. Adjacent thepanel-engaging end face 48 are a plurality of angled or inclined, planaror flat faces or facets 56. It is noted that the outer periphery of thepanel-engaging end face 48 is polygonally-shaped due to the inclinedfaces 56. In the illustrated embodiment, the outer edge of thepanel-engaging end face 48 is octagonal while the inner or shearing edge54 is circular. It should be obvious that for simplicity ofmanufacturing of the die member 44, the outer edge of end face 48 couldbe round and the inclined faces 56 could be one contiguous conicalsurface.

The quantity of the faces 56 of the die member 44 is the same as thequantity of the faces 32 on the bottom wall 26 of the clinch nut 10(FIGS. 1-3) to be installed by the die member 44. The faces 56 of thedie member 44 are sized and shaped to cooperate with the faces 32 of theclinch nut bottom wall 26 as described in more detail hereinbelow. Theangle of the faces 56 of the die member 44 are also sized to cooperatewith the bottom wall 26 of the clinch nut 10. For example, when thebottom wall 26 of the clinch nut 10 is angled about 20 degrees relativeto a plane perpendicular to the central axis 20, the faces 56 of the diemember 44 are preferably angled about 18 to 22 degrees relative to aplane perpendicular to the central axis 50.

FIGS. 6A to 6C illustrate installation of the clinch nut 10 into a metalpanel or plate 58 using the die member 44, typically referred to as the“nut setting process”. The clinch nut 10 and the die member 44 arecoaxially positioned on opposite sides of the metal panel 58 at aposition in which the clinch nut 10 is to be secured to the metal panel58 (best shown in FIG. 6A). The clinch nut 10 and the die member 44 arealso circumferentially oriented so that the inclined faces 32 of theclinch nut bottom wall 26 and the inclined faces 56 of the die memberare circumferentially aligned.

The die member 44 and the clinch nut 10 are relatively moved toward oneanother in an axial direction by any suitable manner such as amechanical press or a hydraulic or pneumatic plunger. It is noted thatthe relative movement between the clinch nut 10 and the die member 44can be achieved by moving either one or both of the components. Therelative movement between the clinch nut 10 and the die member 44 causesthe shearing edges 40, 54 to cooperate to shear or punch an opening inthe metal panel 58 (best shown in FIG. 6B) into which the punch portion14 of the clinch nut 10 extends. The resulting metal slug 60 is forcedinto the central opening 52 in the die member 44.

The relative movement between the clinch nut 10 and the die member 44 iscontinued until the lip 24 of the clinch nut 10 engages the metal panel58 and the panel-engaging end face 48 of the die member 44 forces metalmaterial of the metal panel 58 into the groove 22 of the clinch nut 10.Metal material is coined between the bearing surface of the clinch nut10 and the bearing surface of the die member 44. The coining actioncauses material to flow into recesses in the clinch nut 10 whichenhances retention of the clinch nut 10 to the metal panel 58 to resisttorsional load or push out forces. Material is forced into the undercutat the groove inner wall 28 to improve pull-out strength and is forcedinto the corners formed by the polygonally-shaped groove walls 26, 28,30 and the sides of the lugs 42 to improve torque resistance.

While the width of the die end face 48 is radially smaller than thewidth of the clinch nut groove 22 in the illustrated embodiment, it isnoted that the width of the die end face 48 can be increased so that itextends radially outward beyond the clinch nut 10. This is particularlydesirable when the metal panel 58 is a softer material in order to limitintrusion of the die 44 into the panel 58. It is also noted that whenthe metal panel 58 is a softer material, the lip 24 of the clinch nut 10may intrude the metal panel 58 rather than just engage it as shown inFIG. 6C.

Once the die member 44 is removed, the clinch nut 10 is securelyfastened to the metal panel 58 (best shown in FIG. 6C). The punchportion 14 of the clinch nut 10 extends into the opening formed in themetal panel 58 but preferably does not extend beyond the other surfaceof the metal panel 58. Installed in this manner, a threaded fastener canbe inserted in the threaded opening 16 of the clinch nut 10 to secure adesired item to the metal panel 58. It is noted that this procedure isto secure the clinch nut 10 to thin metal panels 58, that is, panelshaving a thickness of 3 mm or less. For metal panels having a thicknessof greater than 3 mm, the aperture or opening is preferably pre-punchedunless the nut's punch portion 14 and body portion 12 are resized aspreviously described. The remaining methodology for installation is thesame.

FIGS. 7-9 illustrate a self-piercing clinch nut 70 according to a secondembodiment of the present invention wherein like reference number areutilized to indicate like structure. The clinch nut 70 of the secondembodiment is substantially the same as the clinch nut 10 of the firstembodiment described in detail hereinabove except that the lugs 42 areof a different configuration. The clinch nut 70 of the second embodimentillustrates that the lugs 42 can have a different shape.

In the second embodiment, the lugs 42 are formed by protuberances whichaxially extend above the groove bottom wall 26 and radially extendacross the groove 22 from the groove inner wall 28 to the groove outerwall 30. The upper sides of the lugs 42, which are the sides oppositethe bottom wall 26, are generally parallel with the bottom wall 26 andangled or inclined relative to the lip 24. The outer ends of lug uppersides preferably meet the inner edge of the lip 24 but alternatively canbe recessed below the lip 24. The lugs 42 are preferablycircumferentially spaced apart along the bottom wall 26 and preferablythere is a lug 42 centrally located on each face of the bottom wall 26.The cross-sectional shape of the illustrated lugs 42 is rectangular. Thecross-sectional shape of the lugs 42, however, may be any other suitableshape.

For example, an acceptable clinch nut 70 having a thread size of M10×1.5and for work pieces having a minimum thickness of 0.050 inches (1.27 mm)can have a bottom wall 26 with eight facets 32 inclined at an angle ofabout 20°. The facets 32 are aligned with eight facets 34 of the punchportion inner wall 28, eight facets 36 of the outer wall 30, and eightfaces 38 of the body portion outer periphery. The outer wall 30 has aheight of about 0.005 inches to about 0.015 inches. The body portion isabout 0.712 to about 0.730 inches across corners, is about 0.666 toabout 0.674 inches across flats, and has a height of about 0.314 toabout 0.318 inches. The distance between inner edges of the lip 24 isabout 0.600 to about 0.606 inches. The punch portion 14 has a height ofabout 0.043 to about 0.047 inches above the lip 24, a diameter of about0.514 to about 0.518 inches, and a base diameter at the bottom wall ofabout 0.484 inches maximum. The lugs 42 have a width of about 0.058 toabout 0.081 inches.

FIGS. 10-12 illustrate a self-piercing clinch nut 80 according to athird embodiment of the present invention wherein like reference numbersare utilized to indicate like structure. The clinch nut 80 of the thirdembodiment is substantially the same as the clinch nuts 10, 70 of thefirst and second embodiments described in detail hereinabove except thatthe outer wall 30 of the groove 22 is eliminated and the lugs 42 are ofa different configuration. The clinch nut 80 of the third embodimentillustrates that the groove 22 can have a different shape and furtherillustrates that the lugs 42 can have other shapes.

In the third embodiment, the groove 22 is formed by only the bottom wall26 and the inner wall 28. The bottom and inner walls 26, 28 arepreferably sized and shaped the same as described in detail hereinabovewith regard to the first embodiment except that the outer edge of thebottom wall 26 extends to and meets the inner edge of the lip 24. It isnoted that the depth of the groove 22 is reduced when the outer wall 30is eliminated and all other dimensions remain the same.

In the third embodiment, the lugs 42 are formed by protuberances whichaxially extend above the groove bottom wall 26 and radially extendacross the groove 22 from the groove inner wall 28 to the lip 24. Theupper side of the lugs 42, which is the side opposite the bottom wall26, is generally parallel with the bottom wall 26 and angled or inclinedrelative to the lip 24. The lugs 42 preferably have outer end surfaces82 which are parallel and co-planar with the lip 24 so that the lugs 42do not extend above the lip 24. Configured in this manner, the outer endsurfaces 82 of the lugs 42 appear to be inwardly directed extensions ofthe lip 24. The outer ends of the lug lower sides meet the inner edge ofthe lip 24 along the bottom wall 26. The lugs 42 are preferablycircumferentially spaced apart along the bottom wall 26 and preferablythere is a lug 42 centrally located on each face 32 of the bottom wall26. The cross-sectional shape of the illustrated lugs 42 is rectangular.The cross-sectional shape of the lugs 42, however, may be any othersuitable shape.

For example, an acceptable clinch nut 80 having a thread size of M10×1.5and for work pieces having a minimum thickness of 0.050 inches (1.27 mm)can have a bottom wall 26 with eight facets 32 inclined at an angle ofabout 20°. The facets 32 are aligned with eight facets 34 of the punchportion inner wall 28 and eight faces 38 of the body portion outerperiphery. The body portion is about 0.712 to about 0.730 inches acrosscorners, is about 0.666 to about 0.674 inches across flats, and has aheight of about 0.314 to about 0.318 inches. The distance between inneredges of the lip 24 is about 0.600 to about 0.606 inches. The punchportion 14 has a height of about 0.043 to about 0.047 inches above thelip 24, a diameter of about 0.514 to about 0.518 inches, and a basediameter at the bottom wall of about 0.484 inches maximum. The lugs 42have a width of about 0.058 to about 0.081 inches and a thickness ofabout 0.005 inches to 0.010 inches.

FIGS. 13-15 illustrate a self-piercing clinch nut 90 according to afourth embodiment of the present invention wherein like referencenumbers are utilized to indicate like structure. The clinch nut 90 ofthe fourth embodiment is substantially the same as the clinch nut 80 ofthe third embodiment described in detail hereinabove except that thelugs 42 are of a different configuration. The clinch nut 90 of thefourth embodiment illustrates that the lugs 42 can have a differentlocation.

In the fourth embodiment, the lugs 42 are formed by protuberances whichaxially extend above the lip 24 rather than the bottom wall 26 of thegroove 22. The upper sides of the lugs 42 are generally parallel withthe lip 24. The lugs 42 preferably have inner and outer side surfaces92, 94 and end surfaces 96 which are perpendicular to the lip 24. Thelugs 42 each extend along the lip 24 and are spaced apart along the lip24. The lugs 42 preferably have a width generally equal to the width ofthe lip 24. In the illustrated embodiment, the lugs 42 are locatedadjacent alternating faces 32 of the bottom wall 26 and the lugs 42extend a distance slightly longer than the width of each face 32 of thebottom wall 26. The lug outer sides 94 extend the width of a single face32 of the bottom wall 26 and the lug inner sides 92 extend beyond thewidth of a single face 32 of the bottom wall 26 to the outer edge of thelip 24. It is noted that any other suitable quantity, shape, or lengthof the lugs 42 can be alternatively utilized. The cross-sectional shapeof the illustrated lugs 42 is rectangular. The cross-sectional shape ofthe lugs 42, however, may be any other suitable shape. It is noted thatany other suitable quantity or length of lugs 42 can be alternativelyutilized. It is also noted that the lugs 42 can protrude above the lip24 in this manner when the groove 22 has an outer wall 30 as describedin detail hereinabove with reference to the first and secondembodiments.

For example, an acceptable clinch nut 90 having a thread size of M10×1.5and for work pieces having a minimum thickness of 0.050 inches (1.27 mm)can have a bottom wall 26 with eight facets 32 inclined at an angle ofabout 20°. The facets 32 are aligned with eight facets 34 of the punchportion inner wall 28, and eight faces 38 of the body portion outerperiphery. The body portion is about 0.712 to about 0.730 inches acrosscorners, is about 0.666 to about 0.674 inches across flats, and has aheight of about 0.314 to about 0.318 inches. The distance between inneredges of the lip 24 is about 0.600 to about 0.606 inches. The punchportion 14 has a height of about 0.043 to about 0.047 inches above thelip 24, a diameter of about 0.514 to about 0.518 inches, and a basediameter at the bottom wall of about 0.484 inches maximum. The lugs 42have a height of about 0.05 mm to 0.20 mm.

FIGS. 16-18 illustrate a self-piercing clinch nut 100 according to afifth embodiment of the present invention wherein like references areused to indicate like structure. The clinch nut 100 of the fifthembodiment is substantially the same as the clinch nuts 10, 70, 80, 90of the first four embodiments described hereinabove in detail exceptthat the lip 24 and the lugs 42 are of a different configuration. Theclinch nut 100 of the fifth embodiment further illustrates that the lugs42 can have a different configuration and illustrates that the lip 24can have a different configuration.

In the fifth embodiment, the lip 24 has interruptions so that it isformed by a plurality of separate segments each associated with one ofthe faces 32 of the groove bottom wall 26. The separate segments of thelip 24 include alternating narrow and wide segments 102, 104. The narrowsegments 102 generally have a width as described and shown with regardto the first four embodiments. The wide segments 104, however, have anincreased width formed by extending the lip 24 further inward toward theinner wall 28 of the groove 22. The interruptions are preferably groovesformed through the lip 24 generally parallel to the length of the narrowsegments 102. The bottom surfaces 106 formed by the interruptions arepreferably angled or inclined to form extensions of the adjacent bottomwall face associated with the narrow segment 102.

The lugs 42 are formed by protuberances which axially extend above thegroove bottom wall 26 adjacent the wide segments 104 of the lip 24. Thelugs 42 radially extend across the groove 22 from the groove inner wall28 to the lip wide segments 104. The upper side of the lugs 42, which isthe side opposite the bottom wall 26, is generally parallel with thebottom wall 26 and inclined relative to the lip 24. The outer ends oflug upper sides preferably meet the inner edge of the lip wide segments104 so that the lugs 42 do not extend above the lip 24. The lugs 42preferably have a width which extends the full width of the associatedface 32 of the bottom wall 26 such that none of the associated face 32of the bottom wall 26 is exposed.

For example, an acceptable clinch nut 100 having a thread size ofM10×1.5 and for work pieces having a minimum thickness of 0.050 inches(1.27 mm) can have a bottom wall 26 with eight facets 32 inclined at anangle of about 20°. The facets 32 are aligned with the facets 34 of thepunch portion inner wall 28 and the faces 38 of the body portion outerperiphery. The body portion is about 0.712 to about 0.730 inches acrosscorners, is about 0.666 to about 0.674 inches across flats, and has aheight of about 0.314 to about 0.318 inches. The distance between inneredges of the narrow portions 102 of the lip 24 is about 0.600 to about0.606 inches. The distance between inner edges of the wide portions 104of the lip 24 is about 0.537 to about 0.543 inches. The punch portion 14has a height of about 0.043 to about 0.047 inches above the lip 24, adiameter of about 0.514 to about 0.518 inches, and a base diameter atthe bottom wall of about 0.484 inches maximum.

FIGS. 19-21 illustrate a self-piercing clinch nut 110 according to asixth embodiment of the present invention wherein like reference numbersare utilized to indicate like structure. The clinch nut 110 of the sixthembodiment is substantially the same as the clinch nut 100 of the fifthembodiment described hereinabove in detail except that the lugs 42 areof a different configuration. The clinch nut 110 of the sixth embodimentfurther illustrates that the lugs 42 can have different shapes.

The lugs 42 are formed by protuberances which axially extend above thegroove bottom wall 26 adjacent the wide segments 104 of the lip 24. Thelugs 42 radially extend across the groove 22 from the groove inner wall28 to the wide segments 104 of the lip 24. The upper side of the lugs42, which is the side opposite the bottom wall 26, is generally parallelwith the upper side of the lip 24 but is recessed below the lip 24. Theouter ends of the lugs 42 preferably extend less than the full width ofthe lip wide segments 104 and have an increasing width in an inwarddirection toward the inner wall 28. The bottom surfaces 112 formed bythe reduced size of the lugs 42 are preferably angled or inclined toform extensions of the adjacent bottom wall face associated with thenarrow segment 102.

For example, an acceptable clinch nut 110 having a thread size ofM10×1.5 and for work pieces having a minimum thickness of 0.050 inches(1.27 mm) can have a bottom wall 26 with eight facets 32 inclined at anangle of about 200. The facets 32 are aligned with the facets 34 of thepunch portion inner wall 28 and the faces 38 of the body portion outerperiphery. The body portion is about 0.712 to about 0.730 inches acrosscorners, is about 0.666 to about 0.674 inches across flats, and has aheight of about 0.314 to about 0.318 inches. The distance between. inneredges of the narrow portions 102 of the lip 24 is about 0.600 to about0.606 inches. The distance between inner edges of the wide portions 104of the lip 24 is about 0.537 to about 0.543 inches. The punch portion 14has a height of about 0.043 to about 0.047 inches above the lip 24, adiameter of about 0.514 to about 0.518 inches, and a base diameter atthe bottom wall of about 0.484 inches maximum.

FIGS. 22-24 illustrate a self-piercing clinch nut 120 according to aseventh embodiment of the present invention wherein like referencenumbers are utilized to indicate like structure. The clinch nut 120 ofthe seventh embodiment is substantially the same as the clinch nut 10 ofthe first embodiment described hereinabove in detail except that thewalls 26, 28, 30 of the groove 22 are generally circular rather thanfaceted and the lugs 42 are of a different configuration. The clinch nut120 of the seventh embodiment further illustrates that the groove walls26, 28, 30 can have other shapes and further that the lugs 42 can havedifferent shapes.

The groove bottom wall 26 is inclined as described in detailhereinabove, but is now circular without the above described facets. Thebottom wall 26 of the seventh embodiment is generally frusto-conicallyshaped. The inner wall 28 is also inclined as described in detailhereinabove, but is also now circular without the above describedfacets. The inner wall 28 of the seventh embodiment is generallyfrusto-conically shaped. The groove outer wall 30 is circular orcylindrically-shaped. It is noted that this circular shape of the groove22 can be utilized in each of the other embodiments.

The lugs 42 are formed by protuberances which axially extend above thegroove bottom wall 26 and radially extend across the groove 22 from thegroove inner wall 28 to the inner wall. The inner ends of the lugs alsoextend upward along the inner wall 26 or punch portion 14. The lugs 42are generally triangular in cross-section forming a central top edge andhave decreasing widths in the inward direction to form points or tips atthe inner ends of the lugs 42.

FIGS. 1A, 2 and 3A, illustrate a variation of the clinch nut 10 of thefirst embodiment shown in FIGS. 1-3, wherein like reference numbers areutilized to indicate like structure. The clinch nut is substantially thesame as the clinch nut 10 of the first embodiment described hereinabovein detail except that the lugs 42 extend upward along the facets 34 ofthe punch portion 14 above the lip 24. This variation of the clinch nut10 further illustrates that the lugs 42 can upwardly extend along theinner wall 28.

The upwardly extending portion of each lug 42 preferably has an outerside which is substantially parallel with the central axis 20 and, inthe first embodiment, substantially perpendicular to the upper sides ofthe horizontally extending portion of the lugs 42. The upwardlyextending portion, therefore, generally removes the undercut of thepunch portion 14 at the lugs 42.

For example, the above-described specific example of the firstembodiment can additionally have an upwardly extending portion whichextends above the lip 24 about 0.041 inches. It is noted that while thisvariation is specifically shown with regard to the clinch nut accordingto the first embodiment of the present invention, it similarly appliesto the other embodiments having the lugs 42 within the groove and isparticularly advantageous with the second embodiment (FIGS. 7-9) and thethird embodiment (FIGS. 10-12).

Although particular embodiments of the invention have been described indetail, it will be understood that the invention is not limitedcorrespondingly in scope, but includes all changes and modificationscoming within the spirit and terms of the claims appended hereto.

What is claimed is:
 1. A self-clinching fastener for attachment to aplastically deformable metal panel, said self-clinching fastenercomprising a body portion with a central axis and a central punchportion extending from said body portion and coaxial with said centralaxis, said body portion forming a generally annular-shaped end faceadjacent said central punch portion and a groove defined in said endface encircling said central punch portion, said groove having aninclined inner wall forming an undercut and an inwardly inclined bottomwall such that said groove has an increasing depth in a direction towardsaid undercut, said inclined bottom wall being formed by a plurality ofgenerally flat faces, and a plurality of spaced apart lugs encirclingsaid central punch portion and axially extending from said end face,said lugs forming abutments to improve torsional resistance of saidfastener, said lugs having a generally rectangular cross-section formedby generally flat upper sides axially spaced from said bottom wall andhaving a width dimension extending in the direction of fastenerrotation, said abutments having an axial dimension extending from saidbottom wall to said upper side, said width dimension of said upper sidebeing greater dimension than said axial dimension of said abutment. 2.The self-clinching fastener according to claim 1, wherein said inclinedbottom wall is formed by about 6 to about 10 of said generally flatfaces.
 3. The self-clinching fastener according to claim 2, wherein saidinclined bottom wall is formed by eight of said generally flat faces. 4.The self-clinching fastener according to claim 2, wherein said inclinedbottom wall is inclined at an angle of about 20 degrees relative to aplane perpendicular to the central axis.
 5. The self-clinching fasteneraccording to claim 1, wherein said inclined bottom wall is inclined atan angle greater than 2 degrees and less than about 50 degrees relativeto a plane perpendicular to the central axis.
 6. The self-clinchingfastener according to claim 1, wherein said inner wall of said groove isformed by a plurality of generally flat faces aligned with saidgenerally flat faces of said bottom wall.
 7. The self-clinching fasteneraccording to claim 1, wherein said groove further includes an outer wallformed by a plurality of generally flat faces aligned with saidgenerally flat faces of said bottom wall.
 8. The self-clinching fasteneraccording to claim 1, wherein said end face has a lip adjacent an outerperiphery of said groove and said lip is generally perpendicular to saidcentral axis.
 9. The self-clinching fastener according to claim 8,wherein said lugs are located within said groove, said flat upper sidesbeing parallel with the lip and recessed below the lip.
 10. Theself-clinching fastener according to claim 8, wherein said flat facesforming said bottom wall each have a polygonal shape.
 11. Theself-clinching fastener according to claim 10, wherein said polygonalshape is a trapezoidal shape.
 12. The self-clinching fastener accordingto claim 1, wherein said lugs also include an axial portion extendingalong at least a part of said central punch portion with said flat uppersides radially spaced from said inclined inner wall and said abutmentsextending from said inclined inner wall to said flat upper sides. 13.The self-clinching fastener according to claim 1, wherein said generallyflat upper sides are generally parallel with said bottom wall.
 14. Theself-clinching fastener according to claim 1, wherein said lugs arecentrally located on said generally flat faces of said bottom wall. 15.A self-clinching fastener for attachment to a plastically deformablemetal panel, said self-clinching fastener comprising a body portion witha central axis and a central punch portion extending from said bodyportion and coaxial with said central axis, said body portion forming agenerally annular-shaped end face adjacent said central punch portionand a groove defined in said end face encircling said central punchportion, said groove having an inner wall formed by a plurality ofgenerally flat faces and a bottom wall formed by a plurality ofgenerally flat faces that are each substantially polygonally-shaped,said faces of said bottom wall being aligned with said faces of saidinner wall, and a plurality of spaced apart lugs encircling said centralpunch portion and axially extending from said bottom wall of said groovealong substantially the full radial extent thereof, said lugs formingabutments to improve torsional resistance of said fastener.
 16. Theself-clinching fastener according to claim 15, wherein said inner walland said bottom wall are each formed by about 6 to about 10 of saidgenerally flat faces.
 17. The self-clinching fastener according to claim16, wherein said inner wall and said bottom wall are each formed byeight of said generally flat faces.
 18. The self-clinching fasteneraccording to claim 15, wherein said groove further includes an outerwall formed by a plurality of generally flat faces aligned with saidgenerally flat faces of said inner wall and said bottom wall.
 19. Theself-clinching fastener according to claim 15, wherein said bottom wallis inclined at an angle greater than 2 degrees and less than about 50degrees relative to a plane perpendicular to the central axis.
 20. Theself-clinching fastener according to claim 15, wherein said end face hasa lip adjacent an outer periphery of said groove and said lip isgenerally perpendicular to said central axis.
 21. The self-clinchingfastener according to claim 20, wherein said lugs are located on saidlip.
 22. The self-clinching fastener according to claim 20, wherein saidlip is formed by alternating and spaced apart relatively wide segmentsof said lip.
 23. A self-clinching fastener for attachment to aplastically deformable metal panel, said self-clinching fastenercomprising a body portion with a central axis and a central punchportion extending from said body portion and coaxial with said centralaxis, said body portion forming a generally annular-shaped end faceadjacent said central punch portion and a groove defined in said endface encircling said central punch portion, said groove having aninclined inner wall forming an undercut and an inwardly inclined bottomwall such that said groove has an increasing depth in a direction towardsaid undercut, said inclined bottom wall being inclined at an anglegreater than 2 degrees and less than about 50 degrees relative to aplane perpendicular to the central axis, and a plurality of spaced apartlugs encircling said central punch portion and axially extending fromsaid bottom wall of said groove along substantially the full radialextent thereof, said lugs forming abutments to improve torsionalresistance of said fastener.
 24. The self-clinching fastener accordingto claim 21, wherein said inclined bottom wall is formed by a pluralityof generally flat faces.
 25. The self-clinching fastener according toclaim 24, wherein said inclined bottom wall is formed by about six toabout ten of said generally flat faces.
 26. The self-clinching fasteneraccording to claim 23, wherein said inclined bottom wall is inclined atan angle of about 20 degrees relative to a plane perpendicular to thecentral axis.
 27. The self-clinching fastener according to claim 23,wherein said lugs have a generally rectangular cross-section, said lugshaving a generally rectangular cross-section formed by generally flatupper sides axially spaced from said bottom wall, said abutmentsextending from said bottom wall to said upper sides, said upper sidesbeing of greater dimension than said abutments.
 28. The self-clinchingfastener according to claim 27, wherein said lugs include an axialportion that extends along at least a part of said central punch portionwith said flat upper sides radially spaced from said inclined inner walland said abutments extend from said inclined inner wall to said flatupper sides.
 29. The self-clinching fastener according to claim 23,wherein said lugs have a generally triangular cross section.
 30. Theself-clinching fastener according to claim 29, wherein said lugs includean axial portion that extends along at least a part of said centralpunch portion.